The present invention relates generally to governor control fuel injection pumps for use with turbocharged diesel engines and more specifically relates to a hydraulic aneroid control and flow control device therefor to be used with a fuel injection pump assembly.
Under certain speed and load conditions adequate air is not available in a turbocharged engine to correspond with the amount of fuel injected into each cylinder of the engine. Such an overfueling condition creates unnecessary black smoke. For example, in an engine provided with an exhaust driven supercharger the manual governor control can be advanced faster than the engine and supercharger can build up enough speed to provide sufficient air to the combustion spaces of the engine to support complete burning of the fuel being injected therein during a given cycle. Also, as the load on an engine increases until engine speed is decreased from that indicated by the governor setting, the engine governor attempts to regain the engine speed by automatically advancing the engine fuel rack to supply more fuel and reduction in supercharger speed as a result of the reduced engine speed results in insufficient air being supplied to the engine to support complete burning of the additional fuel being injected.
To overcome over-fueling situations and get rid of the unnecessary and objectionable black smoke it has become common to equip the injection pump assemblies with a diaphragm type control unit known as an aneroid which is responsive to intake manifold pressure to limit the movement of the control rack of the injection pump assembly during periods of low manifold pressure. However, many times, particularly in cold weather, over-fueling is required for starting the engine. Therefore, the aneroid is generally provided with a starting fuel control shaft which can be manipulated to deactivate the aneroid so that over-fueling will be permitted for starting.
There have been many suggestions for devices to automatically control the manipulation of the aneroid fuel control shaft. One suggestion for mechanical control is illustrated in U.S. Pat. No. 3,786,794 but this and other mechanical systems are lacking in reliability. A previous hydraulic aneroid control device known to applicant consists of a cylinder and piston mounted on the side of a fuel pump governor housing and connected to the engine oil pump. Upon receipt of oil pressure from the engine oil pump the piston moves the fuel control shaft to the aneroid and engages the aneroid. Since the engine oil comes up to pressure almost immediately upon cranking the aneroid fuel control shaft is shifted almost immediately. The aneroid and fuel control shaft operate such that when the shaft is in the engaged position the aneroid will engage after the fuel rack is pulled back by the governor flyweights. This happens as the engine starts to accelerate from cranking speed. Thus, the engine will have full rack for the first surge of speed, but only for that surge. If the engine should die, the rack cannot go back into the starting fuel position until oil pressure falls off and allows the fuel control shaft to disengage.